Pesticides in Pet Products: Why Your Dog or Cat May Be at Risk

Last June Diane Bromenschenkel applied a flea-and-tick product to her English pointer, Wings, so the dog wouldn't get ticks while hunting pheasant in the tall grasslands of western Idaho. Wings, a healthy five-year-old with a sleek white coat and a chocolate brown mask, enjoyed long walks in the woods, bacon treats, and burying things in the yard. But three months after the pesticide was applied, the animal was dead.

It was just hours following the use of the product that Bromenschenkel knew something was wrong. She noticed her dog walking around in a daze. Wings was unresponsive. On the advice of her veterinarian, Bromenschenkel tried to wash off the treatment —Bio Spot Spot On Flea and Tick Control for Dogs -- but the next day Wings was still suffering.

The dog stopped eating and drinking despite the application of appetite increasers, said Patricia Pence, the veterinarian and owner of South Wind Veterinary Hospital in Nampa, Idaho, where Wings was treated. "The anorexia is a direct result of the Bio Spot," Pence said. She believes the insecticide in Bio Spot damaged the portion of Wings' brain responsible for hunger and thirst. So she inserted a feeding tube into the dog's neck and for the next three months Bromenschenkel and Wings were in and out of the veterinary hospital.

During this period, Bromenschenkel woke up every two hours at night to give Wings an injection of liquid nutrient through the neck. She spent thousands of dollars on vet bills. Despite the best efforts of Bromenschenkel and Pence, however, the damage was done. In September, Wings' kidneys failed and Bromenschenkel made the difficult decision to put her dog to sleep. In days Wings had gone from a healthy dog, running alongside horses in the Owyhee Mountains, to an emaciated wreck, chasing phantom birds in the kitchen. "What's so terrible about it is that if you had known, you would never have used it," said Bromenschenkel of the Bio Spot.

The Debate Over Pyrethroids

Wings died three months after being treated with Bio Spot flea and tick drops; her vet thinks the product damaged the part of Wings' brain responsible for hunger and thirst. Credit: Diane Bromenschenkel. Bio Spot contains a 45 percent solution of the active ingredient permethrin, a synthetic neurotoxin belonging to the pyrethroid family of chemicals. Bio Spot is one of several over-the-counter spot on (meaning squeezed on to a particular spot) anti-flea-and-tick products that consumers apply to cats and dogs between the shoulder blades and sometimes at the base of the tail. The animal's natural oils spread the insecticide over its body, making its skin and fur inhospitable to parasites. These pyrethroid-based flea and tick treatments -- from Hartz, Sergeant's, Farnam, and Bayer -- are approved for sale by the Environmental Protection Agency (EPA), and they are readily available at grocery stores, specialty pet retailers, and hardware stores. But they are also linked to thousands of reported pet poisonings, and they have stirred the ire of pet owners, the concern of veterinarians, and the attention of regulatory agencies.

Manufacturers and distributors of over-the-counter spot on treatments say the products are generally safe and effective when used properly, but they concede there are cats and dogs that either have a preexisting condition or an acute sensitivity to these treatments that leads to an illness.

The industry position, however, may dismiss safety concerns too casually. At least 1,600 pet deaths related to spot on treatments with pyrethroids were reported to the EPA over the last five years, according to an analysis of EPA pesticide incident exposure data by the Center for Public Integrity. That is about double the number of reported fatalities tied to similar treatments without pyrethroids, such as Frontline and Advantage -- although these products also have critics.

Pyrethroid spot ons also account for more than half of "major" pesticide pet reactions reported to EPA over the last five years -- that is, those incidents involving serious medical reactions such as brain damage, heart attacks, and violent seizures. In contrast, non-pyrethroid spot on treatments accounted for only about 6 percent of all major incidents.

In the last five years, the EPA received a total of more than 25,000 reports of pet pesticide reactions of every sort -- fatal, major, moderate, and minor -- to over-the-counter pyrethroid spot on products. This compares to 10,500 reports of all pet incidents related to shampoos, powders, sprays, collars, dips, mousses, lotions, and towels. This analysis does not take into account how much of each product was used over the last five years as the EPA does not have that information.

The EPA cautions that it does not confirm the authenticity of these reports and most of the claims come from consumers and not trained toxicologists. The EPA uses the database to observe broad trends and to identify significant spikes in incidents for specific products and chemicals.

Warning Signs

A few websites, run by pet owners, specialize in educating people on the dangers of over-the-counter spot on treatments. Almost every day someone posts a new horror story, often involving a late-night emergency trip to the vet. "I cannot stop crying knowing that if I hadn't put that on them then they would still be here playing and loving as they always did before," reads one post about a woman's loss of two kittens in October.

The concentrations of pyrethroids in over-the-counter spot on pet treatments range from a 40 percent to an 85 percent solution, eight to 17 times stronger than the strongest pyrethroid product currently approved for use on humans. Neither the EPA, which generally regulates topically applied products, nor the Food and Drug Administration, which generally regulates orally applied pet products, has a product registered for human application containing a pyrethroid concentration above 5 percent, and that FDA-approved product requires a doctor's prescription. In fact, the Sergeant's Gold Squeeze-On for Dogs warning reads: "Harmful if swallowed or absorbed through skin," while the application portion of the label directs people to apply the treatment "to the dog's skin."

But these high concentrations may be necessary in pet products because pets are more apt to come in contact with fleas and ticks, according to Margaret Rice, chief of the EPA's Office of Pesticide Programs registration branch. Some human products, like the 5 percent permethrin shampoo, also call for more of the product to be applied than the just under one ounce in the spot on treatments.

Pyrethroid toxicity targets nerve and muscle cells in pets, according to a study published in The Veterinary Journal in June 2008. The study found that dermal exposure by application to the skin or coat is the most common route of toxic exposure, potentially causing hyperexcitability, tremors, profuse salivation, and seizures. The seizures can result in brain damage or, less frequently, death.

Representatives of Central LifeSciences, the parent company of Farnam, the distributor of Bio Spot, said that they could not discuss the death of Wings because their investigation of the incident is still underway. The company said reports of adverse reactions are rare, about three of every 10,000 doses for cat products and five of every 10,000 doses for dog products. These numbers include incidents that resulted from misapplication and preexisting medical conditions, according to Central LifeSciences. "Bio Spot Spot On Flea & Tick Control for Dogs has met all applicable EPA registration requirements and is approved for topical use on dogs," the company said in a letter they sent in July to one unhappy customer whose dog had recently died.

"Even if it is owner error much of the time, something is not working the way it should be," said Stephanie Shain, director of outreach for the Humane Society of the United States.

Hartz Mountain Corp. representatives said via e-mail that the active ingredient in the company's spot on dog treatments, the pyrethroid d-phenothrin, and the active ingredient in their cat product that kills adult fleas, the pyrethroid etofenprox, are categorized as least toxic by the EPA, as opposed to the active ingredient in Frontline, fipronil, and the active ingredient in Advantage, imidacloprid, which, while much less concentrated, are rated as moderately toxic. Sergeant's cat spot on treatments also contain etofenprox, but the company has spot on dog products that contain cyphenothrin and products that contain permethrin, moderately toxic pyrethroids.

Another possible explanation for the number of incidents is that consumers often misuse flea and tick products, causing the sickness that pet owners later blame on the treatments, said Jennifer Windrum, a spokeswoman for Sergeant's. "Pet owners feel incredibly guilty if they misapply it to their pet," Windrum said. "It's easier to blame a company." Common misapplications include applying more powerful dog products to cats, applying the product where the pet can lick it, and using a treatment meant for a large animal on a small one. The directions on these products include a description of where to apply, sometimes a diagram, and if it's a dog product, multiple warnings not to it use on cats.

Forest Desmond and his wife Marilynn received a letter from Sergeant's offering to pay their $125 vet bill after they applied Sergeant's Gold Squeeze-On for Dogs to their five dogs. The letter from Sergeant's also stated that the company believed the dogs may have licked the product off each other, a violation of the application instructions. "The Sergeant's Gold Squeeze-On for Dogs is for external use only and has several warnings on the package indicating such," the letter says. The product's label does not instruct consumers to keep dogs separated after treatment, but Sergeant's has submitted a request to the EPA to have the label changed. Sergeant's "Look at the Label" website already recommends people separate their pets after application.

"What they're trying to say is the dogs licked it off each other and thereby took it in internally, but they didn't lick it off, it burned their skin," Marilynn Desmond said. "My response to that is they're trying to shift the blame from the producer to the user. If this had been my first dog, I might have fallen for that."

The authors of the study in The Veterinary Journal agree that misuse of pyrethroid products is often the cause of illnesses, although they also point out that accidental ingestion by mouth or during grooming is another common exposure route. "The best way to avoid serious problems is by educating pet owners to use products strictly according to label directions," the study says. "Veterinarians must advise clients using flea care products to read and follow label instructions completely before applying them on or around their pets." The rub here, some veterinarians say, is pyrethroid spot on treatments are over-the-counter products, easily purchased without consulting a veterinarian.

Michael Murphy, a veterinarian and toxicologist at the University of Minnesota, speaking for the American Veterinary Medical Association, said he rarely hears of pet reactions to spot on treatments, and when he does it's usually because a consumer applied a stronger dog product to a cat. But for some pet advocates, the misapplication explanation misses the point. The Humane Society of the United States has heard this reasoning before, but still recommends pet owners avoid over-the-counter spot on products and only use treatments recommended by veterinarians, according to Stephanie Shain, the organization's director of outreach. "With the number of complaints we get it seems like an extraordinarily high rate of problems," she said. "Even if it is owner error much of the time, something is not working the way it should be. I think at the very least there need to be much stronger warnings on those products cautioning pet owners about the dangers involved with using them."

Others express similar concerns. "Sometimes I wonder why it's still approved," said Mark Grossman, a co-owner and veterinarian of Roanoke Island Animal Clinic and a toxicology consultant for the Veterinary Information Network. "They can't get it out there without the EPA approving it. Apparently they say if they do enough tests, it's still OK. In real life though, I think we're seeing more problems than we should."

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Paying the Bills

After Samantha Ribble's English bulldog, Bella, and pug, Chloe, developed oozing sores where she placed drops of Sergeant's Gold Squeeze on for Dogs, she asked Sergeant's to pay her veterinarian bill, $309. Without admitting any liability, Sergeant's agreed to pay the bill, on the condition that Ribble sign a release that read as follows: "I agree not to make any oral or written communication which disparages or has the effect of damaging the reputation of or otherwise working in any way to the detriment of Sergeant's. This Release shall inure the benefit of Sergeant's heirs, legal representatives, successors, and assigns and shall bind me and my heirs, legal representatives, successors, and assigns." In the same letter, Sergeant's notes that its products are closely regulated by the EPA and tested in "accordance with EPA rules and regulations in order to ensure that the products are safe."

This is true. The EPA approved the company's pyrethroid spot on treatments just as it has approved all spot on treatments, but the agency has a history of approving pet products in the past only to pull them from the market later. The EPA approved the use of chlorpyrifos products, cancelled for use on pets in 2001; diazinon products, cancelled for use on pets in 2001; and phosmet products, cancelled for use on pets by 2004. The products were approved, defended aggressively by the chemical industry, and then yanked off the market. They were largely replaced by pyrethroid products, which are generally thought to be less acutely toxic.

Even pyrethroid pet products, however, have been approved and then pulled. In 2000, the EPA received a rash of reports from cat owners concerning Hartz Mountain Corp.'s Advanced Care Once a Month Flea & Tick Drops for Cats, a spot on treatment containing the pyrethroid d-phenothrin. The agency received reports of cats losing their hair, salivating uncontrollably, experiencing tremors, and sometimes dying. Judy Van Wyk of Rhode Island filed a lawsuit against Hartz in November 2001 on behalf of pet owners whose cats had reacted to Hartz cat drops. The complaint alleged that "Hartz has also known since at least March 2001 that adverse reactions in cats to the Drops is a common problem." The suit was voluntarily withdrawn in November 2002, which may indicate an out-of-court settlement, but neither Hartz nor Van Wyk would comment on the case.

Three years later, after the company and the agency experimented unsuccessfully with stronger warning labels, the EPA entered into negotiations with Hartz Mountain Corp. and the company agreed to stop selling the product.

"When we register these products, we feel they're safe," said Marion Johnson, branch chief of the EPA's Office of Pesticide Programs registration division.

Rice, chief of the EPA's Office of Pesticides registration branch, said the agency knows it has had problems with these products in the past. Still the EPA holds the position, as with all products registered by the agency, that pyrethroid-based spot on treatments are not harmful if consumers follow label instructions. The 25,000 reported incidents alone will not change this conclusion, Rice said. The EPA is investigating pyrethroid incidents, involving both humans and pets, and when it finishes this process -- the EPA does not have a target date yet for doing so -- it may make regulatory changes, but until then the agency stands by its conclusion. "Our decisions to register these products and compounds are done with significant data," said Marion Johnson, branch chief of the EPA's Office of Pesticide Programs registration division. "When we register these products, we feel they're safe."

So safe in fact that Johnson said the EPA does not expect any pets will have a sensitivity to spot on products leading to an illness; the incident reports, in Johnson's view, are not at all definitive. Manufacturers, for their part, do acknowledge the existence of sensitive cats and dogs. "There is a certain percentage of dogs out there that, just like with humans, will have an allergic reaction no matter what," Windrum, the Sergeant's spokeswoman, said. Less than 1 percent of sales result in an adverse reaction when the product is used as directed by the label, she said.

The EPA cannot make its own assessment because unlike the regulations directing the FDA's approval of human products, the Federal Insecticide, Fungicide, and Rodenticide Act does not require pet products to undergo field trials prior to approval. So the agency can only require less extensive testing, often only on one breed of dog or cat. This makes it difficult to predict the effects on the broader population of users.

The EPA also considers the need consumers have to control fleas and ticks on their pets and the benefit provided by low-cost pyrethroid spot ons when making decisions about these products. The over-the-counter pyrethroid spot ons are typically half the price of Frontline and Advantage.

EPA scientists continue to monitor the safety of pet pyrethroids. In November, several EPA employees at the Office of Research and Development authored a piece in BMC Genomics, an online journal that publishes peer-reviewed articles, that found exposure to the pyrethroids permethrin and deltamethrin in young rats "could result in detrimental effects on neurological function later in life." The study found this was a possibility even using doses of permethrin that do not cause immediate, acute symptoms. The authors of the article suggested many other avenues of research -- including examining the effects of other pyrethroids on neurological function.

The EPA also hopes to improve the quality of incident reports through an online reporting system for veterinarians that began this fall. In addition, the agency is analyzing pet incidents to identify patterns that may lead to additional labeling or further regulatory action, and reviewing the process of approving pet products to see if changes are warranted.

"We need to make sound scientific decisions," Johnson said. "On the one hand we have the data that says this product might be safe and on the other we have incidents that say it might not be."